Given the problem description, it seems that the balls are already in their desired locations. Ball1 and Ball2 are both in Room1, and the goal is for Ball1 and Ball2 to be in Room1. Therefore, no actions are required. The robots do not need to move or use their grippers to pick up or drop the balls. The current state of the world already satisfies the goal state. 

So, the optimal plan in this case is to do nothing.